1. Field of the Invention
The present invention relates generally to a cleaning method and equipment for dipping an object to be treated, such as a semiconductor wafer or a glass substrate for a LCD, into a cleaning solution, such as a chemical or pure water, to clean the object.
2. Related Background Art
In a typical production process for a semiconductor equipment, there is widely adopted a cleaning equipment for sequentially dipping objects to be treated, such as semiconductor wafers or glasses for LCDs, (which will be hereinafter referred to as xe2x80x9cwafersxe2x80x9d), into a cleaning solution, e.g., a chemical, such as aqueous ammonia (NH4OH) or hydrofluoric acid (HF), and/or a rinsing solution (pure water), which are stored in a cleaning bath, to clean the objects.
As a conventional cleaning equipment of this type, there is widely used a cleaning equipment wherein a cleaning bath for storing therein a cleaning solution to dip objects to be treated into the cleaning solution to clean the surfaces thereof is connected to a pure water supply source by means of a cleaning solution supply pipe which is connected to a chemical storing container for storing therein a chemical, the chemical in the chemical storing container being pressurized by an inert carrier gas, such as nitrogen (N2), to be injected into pure water flowing through the cleaning solution supply line so that a predetermined concentration of chemical is supplied to the cleaning bath to clean the objects.
However, in the conventional cleaning equipment of this type, since the chemical stored in the chemical storing container is pressurized by the inert gas, such as N2 gas, to be injected into the pure water line, the injection speed of the chemical injected into the pure water line is set to be constant, so that there is a problem in that it is difficult to change the injection speed within a short time.
Therefore, there are problems in that it is not possible to quickly and appropriately control the injection speed of the chemical in order to obtain an appropriate concentration of cleaning solution corresponding to the conditions of the objects to be treated, and it is not possible to sufficiently supply the appropriate concentration of cleaning solution corresponding to the conditions of the objects to be treated, so that cleaning efficiency and yields deteriorate.
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a cleaning method and equipment which can improve cleaning efficiency by injecting a predetermined amount of chemical into pure water to use a predetermined concentration of cleaning solution corresponding to the conditions of objects to be treated.
It is another object of the present invention to provide a cleaning method and equipment which can improve treatment efficiency with a simple construction and which can decrease the number of gas-liquid surface passages to decrease the amount of adhered particles and to improve etching uniformity.
In order to accomplish the aforementioned and other objects, according to one aspect of the present invention, a cleaning method comprises the steps of: dipping an object to be treated, into pure water to clean the object; and thereafter, controlling the concentration of a chemical in a cleaning solution which is prepared by injecting the chemical into the pure water, and dipping the object into the cleaning solution to clean the object.
Thus, after the object is dipped in the pure water to be cleaned, when the object is dipped in the cleaning solution, which is prepared by injecting the chemical into the pure water, to be cleaned, the concentration of the chemical in the cleaning solution can be changed to a predetermined concentration within a short time. Therefore, it is possible to improve the chemical cleaning efficiency for the object and it is possible to improve the throughput for the whole cleaning.
The amount of the chemical injected into the pure water may be changed on the basis of the temperature of the cleaning solution to control the concentration of the chemical in the cleaning solution. Thus, the concentration of the cleaning solution can be the optimum concentration based on the environment temperature of the object, so that it is possible to improve the chemical cleaning efficiency for the object and it is possible to improve the throughput for the whole cleaning.
The amount of the chemical injected into the pure water may be changed step-wise during one step, to control the concentration of the chemical in the cleaning solution. Thus, during the step of dipping the object in the cleaning solution, which is prepared by injecting the chemical into the pure water, to clean the object, a large amount of chemical can be injected at the initial stage of the cleaning step to prepare a high concentration of cleaning solution by gradually changing the amount of the injected chemical. Therefore, it is possible to reduce the time for unstable concentration of the cleaning solution diluted by dipping the object, and it is possible to improve cleaning efficiency.
The amount of the chemical injected into the pure water may be changed on the basis of the amount of the pure water supplied, to control the concentration of the chemical in the cleaning solution. Thus, the optimum concentration of cleaning solution based on the amount of the supplied pure water can be prepared by changing the amount of the injected chemical on the basis of the amount of the supplied pure water. Therefore, it is possible to improve the chemical cleaning efficiency for the object, and it is possible to improve the throughput for the whole cleaning.
According to another aspect of the present invention, there is provided a cleaning method for dipping an object to be treated, into a cleaning solution stored in a cleaning bath, to clean the surface of the object, the cleaning method comprising the steps of: a first cleaning step for injecting a chemical, which is diluted to a predetermined concentration with pure water continuously supplied in said cleaning bath, into said cleaning solution and for allowing said cleaning solution in said cleaning bath to overflow to clean said object; a second cleaning step for controlling the temperature of the diluted chemical in the cleaning bath so as to be a predetermined temperature and circulating the diluted chemical to clean the object while the supply of both of the pure water and the chemical is stopped when the concentration of the diluted chemical reaches a predetermined concentration; and a third cleaning step for allowing the pure water to overflow in the cleaning bath to clean the chemical adhered to the object.
Thus, when the concentration of the diluted chemical reaches a predetermined concentration after the chemical cleaning, while the supply of both of the pure water and the chemical is stopped, the temperature of the diluted chemical in the cleaning bath is controlled to be a predetermined temperature, and the diluted chemical is circulated to clean the object. Thus, it is possible to reduce consumption of the chemical, and it is possible to effectively utilize the chemical and to reduce the amount of adhered particles.
The cleaning method may further comprise a step for allowing the pure water to overflow to clean the object before said first cleaning step. Thus, when the concentration of the diluted chemical reaches a predetermined concentration after the pure water cleaning and the chemical cleaning, while the supply of both of the pure water and the chemical is stopped, the temperature of the diluted chemical in the cleaning bath is controlled, and the diluted chemical is circulated to clean the object. Thus, it is possible to reduce consumption of the chemical, and it is possible to effectively utilize the chemical and to reduce the amount of adhered particles.
According to a further aspect of the present invention, a cleaning equipment comprises: a cleaning bath for storing therein a cleaning solution and for allowing an object to be treated, into the cleaning solution to clean the surface of the object; a cleaning solution supply pipe for connecting the cleaning bath to a pure water supply source; a chemical storing container for storing therein a chemical; a chemical supply pipe for connecting the cleaning solution supply pipe to the chemical storing container; shut-off means for selectively opening and closing the chemical supply pipe; chemical supply means for supplying the chemical from the chemical storing container to pure water flowing through the cleaning solution supply pipe; and chemical concentration control means for controlling the concentration of the chemical in the cleaning solution.
Thus, a predetermined concentration of cleaning solution can be prepared within a short time by controlling the concentration of the chemical in the cleaning solution, so that it is possible to improve the chemical cleaning efficiency for the object and to improve the throughput for the whole cleaning.
The cleaning equipment may further comprise temperature detecting means for detecting the temperature of the cleaning solution in the cleaning bath, and the chemical concentration control means may control the concentration of the chemical in the cleaning solution on the basis of a detection signal outputted from the temperature detecting means. Thus, the optimum temperature of cleaning solution based on the environment temperature of the object can be prepared by changing the amount of the injected chemical on the basis of the temperature of the cleaning solution, so that it is possible to improve the chemical cleaning efficiency for the object and to improve the throughput for the while cleaning.
The cleaning equipment may further comprise pure water flow detecting means, provided in the cleaning solution supply pipe, for detecting the flow rate of the pure water supplied to the cleaning bath, and the chemical concentration control means may control the concentration of the chemical in the cleaning solution on the basis of a detection signal outputted from the pure water flow detecting means. Thus, the optimum concentration of cleaning solution based on the environment temperature of the object can be obtained by changing the amount of the injected chemical on the basis of the temperature of the cleaning solution, so that it is possible to improve the chemical cleaning efficiency for the object and to improve the throughput for the whole cleaning.
The cleaning bath may have an inner bath for storing therein the cleaning solution to allow the object to be dipped therein, and an outer bath for covering an outer end portion of an opening portion of the inner bath, and the cleaning equipment may further comprise: a circulating line for connecting the bottom of the outer bath to a cleaning solution supply part provided in the inner bath; and a circulating pump, a temperature control mechanism and a filter, which are provided in the circulating line. Thus, the temperature of the chemical stored in the cleaning bath can be controlled to be a predetermined temperature, and the chemical can be circulated and supplied while carrying out the filtering, so that it is possible to reduce consumption of the chemical and to effectively utilize the chemical.
The chemical supply means may have a diaphragm pump. Thus, it is possible to simply and accurately supply the chemical from the chemical storing container to the pure water flowing through the cleaning solution supply pipe, by means of the diaphragm pump.
The chemical supply means may have gas supply means for supplying a chemical carrier gas into the chemical storing container. In this case, an inert gas may be used as the chemical carrier gas. Thus, it is possible to simply and accurately supply the chemical from the chemical storing container to the pure water flowing through the cleaning solution supply pipe, by means of the chemical carrier gas.
The gas supply means may have a gas supply pipe for connecting the chemical storing container to a gas supply source, and the chemical concentration control means may have gas pressure control means, provided in the gas supply pipe, for controlling the pressure of the chemical carrier gas in the chemical storing container. Thus, if a gas having a pressure preset by the gas pressure control means is supplied to the chemical in the chemical storing container, a predetermined amount of chemical can be mixed into the pure water supplied to the cleaning bath, so that a predetermined concentration of chemical can be stored in the cleaning bath. Therefore, the predetermined concentration of chemical can be supplied to the cleaning bath only by controlling the gas pressure, so that it is possible to remove particles, metal contamination substances or natural oxide films which are adhered to the surface of the object.
The cleaning equipment may further comprise pure water flow detecting means, provided in the cleaning solution supply pipe, for detecting the flow rate of the pure water supplied to the cleaning bath, and the gas pressure control means may control the pressure of the chemical carrier gas in the chemical storing container, on the basis of a detection signal outputted from the pure water flow detecting means. Thus, the fluctuation of the flow rate of the pure water can be detected by the pure water flow detecting means, and the gas pressure control means can be controlled on the basis of the detection signal of the pure water flow detecting means, so that it is possible to supply an accurately controlled concentration of chemical to the cleaning bath.
The chemical carrier gas may be an inert gas. Thus, it is possible to maintain a chemically stable chemical carrier gas.
The gas supply means may have a gas supply pipe for connecting the chemical storing container to a gas supply source, and the cleaning equipment may further comprise a gas control branch line of a plurality of shut-off means and diaphragm mechanisms which are provided in the gas supply pipe, each of the shut-off means being selectively open and closed. In this case, the gas control branch lines may be arranged in parallel or in series. Thus, the gas pressure control range can be increased by selectively opening and closing each of the shut-off means. Therefore, it is possible to supply an accurately controlled concentration of chemical to the cleaning bath.
The cleaning equipment may further comprise, liquid level detecting means provided on the chemical storing container, and the chemical concentration control means may control to maintain the liquid level of the chemical in the chemical storing container to be always constant on the basis of a detection signal outputted from the liquid level detecting means. Thus, the amount of the chemical stored in the chemical storing container can be maintained to be constant. Therefore, the amount of the chemical injected into the pure water can be maintained to be constant without being influenced by the amount of the stored chemical, and the concentration of the chemical can be maintained to be constant.
The chemical storing container may comprise a tank which has a circular cross-section and a height of less than or equal to the diameter of the tank. Thus, the influence of the fluctuation of the amount of the chemical stored in the chemical storing container can be restricted, so that the amount of the chemical injected into the pure water can be maintained to be constant.